By now you probably know the arguments for the monitored, controlled, legalized forms of wildlife hunting. It has the potential to reduce conflict with humans and can provide much-needed revenue to be put toward conservation efforts. But not all populations are created equal; applied to the wrong ecosystem, hunting can also drive population declines, the echoes of which will reverberate throughout its landscape. In this week’s issue of Science Magazine, a group of researchers led by Montana State University wildlife biologist Scott Creel argue that wolf hunting policies in the US don’t align with the best evidence that science has to offer.

After wolves were reintroduced to the Northern Rocky Mountains (NRM) in the mid-1990s, the carnivore population grew stronger. But that trend stopped in 2009. That’s because in 2008, the population lost its protection under the ESA and hunting became legalized.

Reviews by the USFWS say that hunting “has not increased any risk” to the NRM wolf population, but Creel and his colleagues aren’t so sure. “Current policies state that half of a wolf population can be shot annually without causing the population to decline,” said Creel in an official statement. “On the basis of ecological theory, this suggestion is not likely to be correct for the wolf, or indeed for any large carnivore.”

Fully-grown, mature large carnivores usually have low mortality rates. They are the kings of their jungles, after all. Hunting doesn’t substitute for other causes of wolf death, as is more likely the case for ungulates like deer. For animals like wolves, hunting pressures instead add to the mortality rate. After hunting was legalized in Montana and Idaho in 2008, wolf pack size there declined by nearly a third. And hunting doesn’t just impact group size – it also affects a group’s social order, which impacts the likelihood that juveniles will grow to reproductive age. Indeed, in 2013, five years after hunting was legalized, hunters took 25% fewer wolves – despite an extended hunting season!

How can the scientific evidence and the USFWS review be so contradictory? Creel’s group suggests that there can be a mismatch between the animals that provide the data to inform policy decisions and the animals to which that policy applies. “Carnivore distributions do not follow political borders, but hunting policies do,” they say. Just because the overall Northern Rocky Mountains population has been relatively stable under pressure from hunting doesn’t mean that the packs in any given state are equally so. Idaho’s annual wolf counts declined by nearly a quarter between 2008 and 2013.

More importantly, Creel’s group says the studies on which the USFWS based their review focused on wolf populations that could recruit immigrant wolves from other, nearby populations. Those local losses to hunting could be replaced by the influx of new individuals from elsewhere. It’s not that wolves are able to compensate for local losses, but it might appear that way if you’re not looking very closely. By analogy, while African lions may be protected within national parks, legalized hunting just outside of parks can still destabilize the overall lion population. Harvesting lions outside of parks creates a “vacuum,” drawing in the otherwise protected lions from inside of parks – leaving them vulnerable to hunting.

There can be a sustainable way forward for carnivore hunting. The future of wildlife management in most parts of the world probably includes at least some carefully controlled harvest. But if legalized hunting is to occur, the researchers say that policies need to be based on rigorous, empirical science, which requires “clearly defined, quantitative” goals.

Current wolf hunting policies in the NRM simply aim to avoid a population crash so severe that it would require re-listing under the ESA, but that’s too hand-wavy a target. Instead, policies should specify things like maximum harvest rates or goals for population size or growth from year to year. According to Creel, “the North American model of wildlife management works very well for species like ducks or elk, but becomes much more complex for species like wolves that compete with hunters.” – Jason G. Goldman | 18 December 2015